低韦伯数非牛顿射流撞击破碎直接数值模拟

Direct numerical simulation of impinging jet breakup with non-Newtonian properties at low Weber number

非牛顿射流的撞击破碎在液体火箭推进系统中被广泛用于燃料的喷注雾化,然而人们对其破碎物理机制却知之甚少。本文将采用基于液体体积法的直接数值模拟(DNS)工具,研究夹角为90°的2个等直径低韦伯数射流撞击现象,并分析二者形成的单一对角射流特征及其破碎机理。研究结果表明,撞击形成的单一对角射流直径较原射流直径大1.66倍,并在头部形成液滴诱导破碎的发生。除了头部破碎,在对角射流的发展过程中还观察到一类液柱破碎,表现为射流表面不稳定波不断发展形成新的弯曲波破碎,并产生卫星液滴及液滴的融合。伴随两股射流撞击的发生,气液两相交界面的面积也不断减小,同时,射流内部的黏性也不断变化,在本文的低雷诺数和低韦伯数条件下,流体内部黏性系数变化超过10%。

Impinging jet breakup with non-Newtonian properties has been widely applied in the liquid rocket propulsion system for fuel atomization.However,the basic breakup mechanism of the phenomena still remains unsolved up to now.In the present work,a direct numerical simulation（DNS）based on the volume of fluid method is carried out to investigate the impinging phenomena of two orthogonal identical liquid jets,and to analyze the characteristics and the breakup of the resulted diagonal jet.The results indicate that the diameter of the diagonal jet is 1.66 times larger than that of the original jet.The head breakup can be observed near the jet tip,and the column breakup can be also observed.Due to surface wave development,wavy breakup is generated with the formation of satellite droplets and droplet collision.During the impinging process,the total surface area of the liquid decreases.The local viscosity of the shear thinning liquid decreases as well.Under the condition of low Reynolds and Weber numbers in the present work,the local viscosity varies over 10% spatially.